Centrifugal compressor operation

[AidanSayers]

I have an electric motor driven centrifugal compressor. It is constant speed and is controlled by suction throttling, whcih is manually set. What will be the likely affect if the suction pressure rises, assuming the suction throttling valve stays in position? The comrpessor normal operation inlet pressure is 6barg and discharges at 9barg. The maximum suction pressure could be the relief pressure of the suction drum (10barg). However, there is a relief valve on the outlet of the compressor set at 13.6barg. Using the standard compressor gas formula, I have determined that, for 10barg suction, the compressor could discharge at 15barg - this is clearly above the relief valve pressure and, hence, not possible. Would the flow reduce to match the max outlet pressure, or would the inlet pressure be less than 10barg?

Any help greatky appreciated.

Aidan Sayers

 

[quark]

Centrifugal compressors are not positive displacement type and you cannot calculate dischrge pressure by standard formulae.(I mean Gas Equations)

Best thing is to refer to compressor performance curve.With reduction in dP, flow will increase.

Regards,

 

[pmover]

in addition to quark's comments, contact the mfg and obtain performance curves for a pressure above and below the design conditions. this will provide you a valuable aid in the overall predicted performance of the unit. another technique is to actually test the unit while in operation, which is preferred and you've obtained a reference condition.
good luck!
-pmover